Secondhand Smoke Riskier than Cholesterol

Action Points

In this study there was a very significant and independent dose-response relationship of secondhand tobacco smoke exposure to coronary artery calcification in never smokers.

The second hand tobacco smoke exposure odds ratios were higher than for all risk factors except male gender and age.

The risk of clogged arteries is greater from secondhand smoke than from several well-known heart disease risk factors, including high cholesterol, researchers found.

The overall prevalence of coronary artery plaque in those exposed to secondhand smoke was 24%, which rose to 26% in those with the highest exposure compared with 19% for the general public, Harvey S. Hecht, MD, of Mount Sinai Medical Center in New York City, and colleagues reported online in JACC: Cardiovascular Imaging.

Those with the highest amount of exposure to passive smoke were 90% more likely to have coronary plaque compared with the general public, (1.93, 95% CI 1.49 to 2.51, P<0.0001).

Even after adjusting for other cardiovascular risk factors, the odds associated with developing coronary disease from secondhand smoke were greater than from other well-established danger signs:

Diabetes – OR 1.88 (95% CI 1.30 to 2.71, P=0.0008)

High cholesterol – OR 1.55 (95% CI 1.27 to 1.89, P<0.0001)

Hypertension – OR 1.42 (95% CI 1.15 to 1.75, P<0.0001)

Renal disease – OR 1.31 (95% CI 0.66 to 2.60, P=0.45)

The only factors that carried more risk of developing arterial plaque were male sex (OR 2.45, 95% CI 2.03 to 2.96, P<0.0001) and advancing age (OR 1.09 per 10 years, 95% CI 1.08 to 1.10, P<0.0001), Hecht and colleagues wrote.

Although previous studies have shown a marked increase in cardiac events related to secondhand smoke, the authors said this study is the first to demonstrate a clear dose-response relationship between secondhand smoke exposure and the earliest detectable signs of heart disease.

"This research provides additional evidence that secondhand smoke is harmful and may be even more dangerous than we previously thought," Hecht said in a statement.

He also said that inquiring about secondhand smoke exposure should be part of every routine exam.

To gather the information for the study, the investigators went to the Flight Attendant Medical Research Institute International Early Lung Cancer Action Program CT, a lung screening program.

They had data for 3,098 asymptomatic people who had never smoked and who were in the screening program between 2005 and 2012.

Participant ages ranged from 40 to 80 and everyone underwent a series of low-dose CT scans as part of the lung screening program.

As part of the screening program, participants had answered detailed health questionnaires that included exposure to secondhand smoke during childhood and as an adult.

The researchers created four categories of exposure: minimal (that seen in the general public), low, moderate, and high. They then assigned a total secondhand smoke exposure score based on how long participants were exposed (in years), daily intensity (packs per day), and if smokers were allowed to smoke anywhere or if they were restricted or not permitted (permission status).

Hecht and colleagues found that exposure itself was an independent predictor of the prevalence of coronary artery plaque, and as the duration and intensity of exposure increased, so did the risk of having diseased arteries.

Low exposure -- OR 1.54 (95% CI 1.17 to 2.02, P=0.002)

Moderate exposure -- OR 1.60 (95% CI 1.21 to 2.10, P=0.0008)

High exposure -- OR 1.93 (95% CI 1.49 to 2.51, P<00001)

They also determined that exposure as an adult was more significant than exposure during childhood.

Those with higher levels of exposure tended to be older, women, and have high cholesterol as well as hypertension and diabetes.

The study was limited by the nature of self-reported data and being retrospective.

Hecht will present the study at the American College of Cardiology meeting, which begins March 9 in San Francisco.

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